mupdf-gl port warnings shown when using mupdf-gl to display a pdf file

[contextnerror ​]

This seems to be caused by not using the included version of freeglut.
https://git.ghostscript.com/?p=mupdf.git;a=commit;h=06c999fec01863a90824ba2f9f3ce98ea1a967d3

> On Oct 16, 2023, at 1:26 PM, Kenneth Wolcott <kennethwolcott at gmail.com> wrote:
> 
> Hi;
> 
>  I recently installed the mupdf port.  The pdf output looks great,
> but a nit: the following warnings are generated when using mupdf-gl to
> display a pdf file.
> 
> warning: This version of MuPDF has been built WITHOUT clipboard or
> unicode input support!
> warning: Please file a complaint with your friendly local distribution manager.
> 
> Thanks,
> Ken Wolcott